The invention relates to a planar Schottky diode with a high limit or cut-off frequency inserted in a transmission line.
A Schottky diode for high cut-off frequency inserted in a transmission line is known from the publication "IEEE Transactions on Microwave Theory and Technique", Vol. MTT25 (1977), pages 494-95, incorporated herein by reference. The Schottky diode described there consists of a single Schottky metal semiconductor contact which is inserted on the substrate body between the leads applied on the surface of the substrate body. When the Schottky diode is inserted into a line with defined characteristic impedance, in higher frequency ranges, it should, if possible, not disrupt the characteristic impedance, for example 50 ohms or 60 ohms, of the line. In this known Schottky diode, the one lead of a band-shape is designed to taper toward the Schottky contact.
A Schottky diode that is designated as an edge diode is known from the publication "IEEE Transactions on Electron Devices", Vol. ED-22 (1975), pages 198-99, incorporated by reference herein. In this known Schottky diode, a Schottky contact extending at right angles to the transmission line is provided which is formed with the end-face surface of an n-doped gallium arsenide layer applied to a substrate.
An edge diode as mentioned above can only be manufactured with relative difficulty in reproducible manner with parameters held within narrow limits. In particular, narrow tolerances for the doping and the doping gradient in the area of the frontface surface of the Schottky contact cause difficulties.
In order to achieve a high cut-off frequency, not only a relatively small capacitance must be achieved for a Schottky diode like the one under discussion here, but, rather, the series and contact resistance occurring in the course of the transmission line must also be held as small as possible.